Sending prayers your way. It sounds like you have so much on your plate right now.
Please, take care of yourself. Try not to overextend yourself (I know it is easy to say and difficult to do.) Your sister is in good hands right now. You must make sure you are cared for in order to be there for your family.
And, if this is hereditary as you said, make your doctor's appointment.
Best wishes to all of you.